Sintered hard metal alloy



United se raemi SINTERED HARD METAL ALLOY Bo 'Gisner and Fall Johan OlofWilliam Ohlsson, Stockholm, Sweden, assignors to Sandvikens JernverksAktiebolag, Sandviken, Sweden, a corporation of Sweden No Drawing.Application April 11,1957 Serial No. 652,101

Claims priority, application Sweden April 13,1956 3 Claims. c1. 29-182.7)

The present invention relates to a sintered hard metal alloy having ahigh wear resistance and great tenacity and being adapted for cutting(machining) material, e.g., steel, which give long chips, which sinteredhard metal alloy is of the type consisting substantially of tungstencarbide, titaniumcarbide, tantalum and/or is lower than 100-1.55.1 Thequantityiof then-phase depends on the content of the auxiliary metal andis normally within the range 10.515% and may expediently be within thenarrowerrange 11-14%. -The? amounts of the-various phases u, ;fl'and arealways represented 1 volume-percentages throughout the specification.

niobium carbide and an auxiliary or bonding metaliolf alloy selectedpreferably from the iron group ofthe periodic table, for instancecobalt, nickel and/or iron.

This type of alloy has a structure built up of the following phases: aa-phase consisting of WC,: a 'y-phase consisting of a solid solution ofWC and TaC/NbC in basis of the present invention) that if thecomposition and structure of such an alloy is chosen within specialrelatively narrow ranges the alloy exhibits a surprising increase inwear resistance and toughness. Alloys according to the present inventionhave been found to; be particularly suitable for machine tools forcutting materials like steel giving long chips, but are not limited tothis particular application. If an alloy according to the invention isused as a cutting tool for turning operations, the same permits highercutting speeds and/or greater rate of feed and cutting depth. Likewisean alloy according to the invention is suitable for machining of steelunder unfavorable conditions, as in relatively unstable machines, ormachining with interrupted cuts, in which operation a better life forthe .hard metal insert is obtained than has been realizedheretoforezlvery good results in comparison with previously known alloyshav also been obtained in the milling of steel.

According to this invention. a sintered hard metal alloy comprises inaddition to WC, substantially 18-21 by weight TiC, 14-18% by weight TaCand/or NbC and 85-11% by weight of auxiliary or bonding metal such asCo, Ni and/ or Fe, the amount of the fl-phase of the alloy and theamount of the -phase being related to one another by the relationship100-1.-2,B 'y 100-2.5;9, wherein p and 7 represent the amounts of'therespective phases expressed in volume percent.

It should here be mentioned that where in this specification and theaccompanying claims we use the expression Ta'C/NbC the same is intendedto convey that the alloy contains either or both the compounds TaC andNbC, and that where a percentage figure is given against the expressionTaC/NbC. this refers to the content of (TaC+NbC) in the alloy.

The alloy may have a structure in which the amount of 'y-phase exceeds100-2 3. and atthesame time is lower than 100-1.2 3; and in many casesthe amount of 'y-phase In comparison with the other known hard metalalloys ofthis kind, the alloy Qofthisinvention hasan increased amount of'yand fi-phase. This'has been'shown to be of great importance forobtaining a high quality alloy creased toughness. 111 1 1 t 1 1 "In someofthe previously known'hardmetal alloys which have been used the amountof the 'y-phase has been lower than lOO-Zfl'and similarly the TiC, TaCand Co contents have been considerably lower than the characteristiclimits required for the alloy of this invention.

' with increased wear resistance and at the same time in- In comparisonwith these known alloys, the alloy of the present invention shows animprovementboth in resistancetowear and ,in toughness. For instance,practical tests have shown that by turning inalathewith ahard metal.alloy in'. accordance with this invention. there has beer'robtained anincrease in the number of'machined detailsofiup to 160% between there-grindings. 1

The r increase. in .content of the I'y-phase may be obtained in'variousmanners. .Thus, the carbide powder to be sintered may consistsubstantially-of carbides in solid solution withllea'ch other, theso-called double carbides (Ti, -W)C, and/or triple carbides (Ti,-Ta,W)C. Itis also possible to-regulate the content of the 'y-phase byadjusting the sinterin'g;'ftemperature and/or sinte'ring time. Forexample, with a rise in -the sinteringtemperature and/ or extension ofthe sintering time a greater quantity of the free tungsten carbide,i.e., the d-phase,

may be dissolved in the-'y-phase and is, with a suitablerate of cooling,kept in-the 'y-lattice. 1 t

The increase incontent of the p-phase,fi.e the auxiliary metal content,is made possible by means of the relatively high content of TaC/NbC,which prevents the plastic deformation which (in connection with highcontents of "auxiliary metal) otherwise a'ppearsj such? plasticdeformation being particularly noticeable in the machining of steel withhigh cutting speeds and feeds. 7 1

For obtaining these unusual properties for the hard metalalloy'according to'thi s invention the stoichiometrical composition ofthe alloy is of'g'reatimportance, the limitsof which have been indicatedabove.

carbide and TaC/ NbC of the hard metal alloy is within the limits 18-23%by weight TiC and 141-18% by weight TaC/NbC, respectively. The amount ofthe auxiliary metal, which advantageously consists of cobalt or ismainly cobalt, is preferably chosen within the range -11% by weight andoften within therange 9 -11-% I y h t r p Especially good propertieshave been obtained for hard metal alloys containing 18-21% by weightTiC, 1418% by weight TaC/NbC and 9-10% by weight Co.

The invention will now be described in greater par- 9.5% Co Remainder WCThe above components, in the relative amounts stated,

were ground together to such a grain size that the ensuing 2,924,875 lfatented Feb. 16, 196( However, it i v is generally advantageousif thecontent of titaniumsintered hard metal alloy product had a grain size of23,u. The finely ground mixture was, after being compressed, sintered ina vacuum oven at about 1500" C. for about one hour.

This alloy consisted of 6.9 volume-percent of a-phase, 82 volumepercentof 'y-phase and 11.1 volume-percent of ,B-phase.

With this alloy tests were carried out with coarse turning of 10.5 cm.shells and on the average 142 shells per re-grincling were machined ascompared with 50 shells with the previously known best grade, i.e., agrade of convention type consisting of 15% TiC, 7% Co and the remainderWC. 7

Example 2 Milling tests were carried out with the alloy, according tothe invention described in Example 1, with the following results:

Material: .Hardened and tempered steel containing (by Weight) C=O.4OSi=0.30%, Mn=0.60%, CI =0.8% and Ni=l.2%. H about 220 (Brinellhardness).

Tools: Milling cutter with six sets of cutting inserts to give six cuts,every other set being of hard metal in accordance with the invention(sintered hard metal according to the analyses and data in Example 1),in the following table designated A, and the other alternate sets beingof hard metal of the conventional type containing 15% (by weight) TiC,7% (by weight) Co and the remainder WC, and in the following tabledesignated B. Average wearland is the wear on the clearance side of thehard metal tool bit.

Cutting data Average Number Efieetive wearland of chipped milling in mm.cutting cutting Feed, Cutting time in edges speed, mm./ depth minutesmJmln. cutting in mm.

insert B A B A.

Grade A, according to the invention, with the milling tests which werecarried out, showed itself to be superior to B in many respects. Thiswas true both as to toughness and resistance to wear. The amount ofcutter wear was remarkably low and even for A, and concerning toughnessin contrast to the relatively coarse chipping appearing on B A wascompletely undamaged.

Example 3 Tests were performed in a thread machine as stated below:

Machine: Thread machine (Cri-Dan make). Type B,

Machine detail: Spindle.

Material: Hardened and tempered chrome-nickel steel, containing (byweight) C=0.3%, Si=0.3%, M:0.8%, Cr=0.8% and Ni==1.3%. H about 285(Brinell hardness).

Operation: Thread cutting M 16 x 1.5, length 20 mm.

Number of cuts: 14.

Cutting speed: 90 m./min.

Hard metal grades: A was the hard metal alloy according to the inventionmentioned in Example 1, B was the previously known best grade for theabovementioned operation, containing 22% (by weight) TiC, 9% (byweight). "Co, and the remainder WC, and C was a hard metal alloy,containing 19% (by weight) TiC, 3% (by weight) TaC, 8.5% (by weight) Co,and the remainder WC.

Two tests were made with grade A. in these tests before the cuttinginsert had to be m-ground.

With grade B, on an average, about details were threaded perre-grinding.

Grade C gave the result 42 and 52 details respectively threaded perre-grindirtg.

Examplet4 An alloy having the followingcornposition by'weight:

The remainder WC, and containing in volurnepercent 11.5% a-phase, 78%'y-phase and 10.5% B-phase was prepared in the manner described inExample 1 above. This alloy was tested by turning of spindle sleeves ina Fischer lathe against a hard metal alloy grade containing 18.5%(by-weight) TiC, 2% (by weight) TaC, 1% (by weight) NbC, 9% (by weight)Co.and.the remainder WC. The cutting speed was m./min., the feed 0.36nun/revolution and the cutting depth 311 mm. The tools in both casesconsisted of steel holders with clamped hard metal alloy inserts. Thegrade according to the invention gave about an.80,%. better result thanthe other grade.

Example 5 Composition by weight:

25% TiC 12% TaC 11% Co Remainder WC The --al loy contained in volume 3%a-phase, 85% phase and 12% B-phase. This .alloy was tested in the mostwidely ditfering machining operations and also with different steelgrades and proved to possess a very high toughness in combination with averysgood resistance to wear.

Example 6 Still another alloy according to the invention which has givenvery good results contained approximately (by weight):

19% TiC 6% TaC 6% NbC 9.5% Co Remainder WC In the manufacture of alloysaccording to the invention it has proved advantageous to includetitanium carbide in the form of the so-called double carbide (Ti,.W)C,containing for example 50% titanium carbide and 50% tungsten carbide.Tantalum and/ or niobium carbide may either be added in the formofsimple carbides or in the form of a solid solution (Ta, Nb)C. Ofcourse it is also possible to include carbides in other solid solutions,for example in the form of (Ti, Ta, W)C. The above-mentioned amountsofthe components are ground together with tungsten carbide and cobalt toa grain size, which will give the sintered 'hard metal alloy product agrain size of preferably 2-3 Pressed components of this powder aresuitably sintered-in a vacuum. oven at about 1500'C. for about 1 hour.

We claim:

1. A sintered hard metal alloy especially for machining steel consistingessentially of the following components in the following percentages byweight: .TiC 18-21%; a carbide of the group consisting of TaC and NbCand mixtures of TaC'and NbC,:14 -18%'", the content of said carbidebeing less than thexcontent of TiC; auxiliary bonding metal of the groupconsisting of Ni, Co and Fe, 85-11%; the remainder being substantiallyall WC, said alloy being further characterized in that and the sum ofthe amounts of the three phases a-, [3- and 'y-equalling 100, where a,,8 and 7 represent the amounts of the respective phases in volumespercent.

2. Sintered hard metal alloy according to claim 1, 15 2,198,343

wherein the bonding metal consists of Co, and the content by weightthereof is within the range 910%.

3. Sintered hard metal alloy according to claim 1, and havingsubstantially the following composition by weight:

19% TiC 12.8% TaC 3.2% NbC 9.5% Co Remainder WC References Cited in thefile of this patent UNITED STATES PATENTS Comstock Sept. 11, 1934Kiefier Apr, 23; 1940

1. A SINTERED HARD METAL ALLOY ESPECIALLY FOR MACHINING STEEL CONSISTINGESSENTIALLY OF THE FOLLOWING COMPONENTS IN THE FOLLOWING PERCENTAGES BYWEIGHT: TIC 18-21%, A CARBIDE OF THE GROUP CONSISTING OF TAC AND NBC ANDMIXTURES OF TAC AND NBC, 14-18%, THE CONTENT OF SAID CARBIDE BEING LESSTHAN THE CONTENT OF TIC, AUXILIARY BONDING METAL OF THE GROUP CONSISTINGOF NI, CO AND FE, 8.5-11%, THE REMAINDER BEILNG SUBSTANTIALLY ALL WC,SAID ALLOY BEING FURTHER CHARACTERIZED IN THAT SOLUTION, TIC, OF ALL OFTHE CARBIDE OF THE GROUP CONSISTING OF TAC AND NBC AND MIXTURES OF TACAND NBC AND SUBSTANTIALLY ALL OF THE WC AND AN A-PHASE CONSISTING OF THEREMAINING UNDISSOLVED WC AND A B-PHASE CONSISTING OF THE AUXILIARYBONDING METAL, THE AMOUNT OF THE B-PHASE THEREOF AND THE AMOUNT OF THEY-PHASE THEREOF BEING RELATED TO ONE ANOTHER BY THE RELATIONSHIP